1. Field of the Invention
The present invention relates to nuclear magnetic resonance tomographic devices, and in particular to a probe for such a device for introducing a measuring coil into organs of an examination subject.
2. Description of the Prior Art
Nuclear magnetic resonance tomographic devices for representing partial regions of the interior of an examination patient are known in the art which utilize coils for generating a basic magnetic field and a potential gradient field, and a measuring coil for detecting the deflection of the nuclear spin of the examination subject from its position of equilibrium by means of high frequency magnetic excitation pulses such as 90.degree. HF pulses and 180.degree. HF pulses.
An apparatus of this type is described in German patent application No. P 31 35 33 5.5. In this apparatus it is possible to deflect the nuclear spins of the atoms of an examination subject from a preferred direction, produced by the basic magnetic field, by means of a high frequency excitation pulse. During the perturbation of the nuclear spin occurring after the excitation pulse, that is, during the procession of the nuclear spin, a signal is generated having a frequency which is dependent upon the intensity of the basic magnetic field. By superimposing a field gradient on the homogeneous basic magnetic field, such that the magnetic field distribution varies spatially, it is possible to designate location of various objects by the individually measured frequency. In this manner, as well as by changing the direction of the field gradient, tomographic images of the examination subject are produced. The nuclear excitation in a layer of the examination subject occurs such that the basic magnetic field is influenced by the additional field gradient such that excitation of the nuclear spins occurs only in the selected layer or slice. This can be achieved because the excitation occurs only at a frequency which is precisely matched with the magnetic field in the desired layer.
Apart from tomographic technology, it is known to implant radioactive substances directly in a tumor cell for localized treatment of tumor cells in the human brain. The implantation proceeds by means of small diameter plastic cannulae which are inserted by surgery in a stereotaxic operation. It is also known to examined body organs such as the liver and the kidney with the aid of a hollow biopsy needle.